Nonaqueous electrolyte secondary batteries, especially lithium ion secondary batteries, each of which has a high energy density, have been widely used as batteries for use in, for example, a personal computer, a mobile phone, and a portable information terminal. Further, nonaqueous electrolyte secondary batteries have recently been being developed as on-vehicle batteries.
As a nonaqueous electrolyte secondary battery separator, Patent Literature 1 discloses a laminated separator including a porous layer formed by coating a polyolefin porous film with a heat-resistant resin.
Meanwhile, Patent Literature 2 discloses a laminated separator including a porous layer formed by coating a polyolefin porous film with a resin and a filler made of a ceramic powder.